Are deep cycle lead acid datasheets a scam? - Page 1
Forum section: electronics / general

author: paulca
author_rank: Super Contributor
timestamp: April 28, 2025, 02:18:59 pm
content: A friend has a mobility scooter. He is getting the expected range, but the batteries basically die after 6 to 10 months. Range plummets to 10-15% over winter and does not recover afterwards.Doing a bit of digging for him, to find out how hard he "should" push them regardless of what the "dealership" says... I found the likes of Bosch and Yuasa claiming... 300 cycles to 80% capacity for a 85% DoD.I mean, yes, sure, maybe, but most likely not.My experience with A Yuasa deep cycle was very different. I got about 100 cycles out of it before it "capacity tested" at 4Ah when it was a 20Ah DC leisure battery being used for a micro solar power setup. ( drained it at 1Amp with a digital load to 12V, recharged with a 1 hour absorb at 14.50V (as rated) and then repeated 3 times. The average was 4Ah. It had done about 100 cycles with the cut out voltage of 11V).I tried multiple things, deep disharging it with a 20mA LED to 11V and then rapid charging it. I tried letting it absorb for hours I tried floating it for days. It was dead. Went in the pile of dead lead acids at the back of the garage. The same place at least one car battery ends up every 2-3 years.Has anyone ever actually experienced daily use, all year round, outdoor lead acids driven down to 15% charge to last longer than a year? Has anyone ever seen them hit the 300+ cycles the datasheet claims? It claims 300 cycles to like 80% capacity. Im talking about 300 cycles to 20% capacity being the reality.I also believe, though have limited tests personally, that "shallow cycling" them leads to "memory effect" and another reduction in capacity that's hard to remove.I advised my friend that after the manufacturer break in, don't "routinely" run it "full range" and "limp home". Do that "once in a while". The rest of the time try not to run it beyond 50% range. When it's under 10C outdoors don't run it past 50% ever. When it's less than 0C, leave it on the charger with the cover over it, stay home.If it wasn't a "Lease deal" I would help fund and replace the batteries with lithium, but ... it is a lease deal.

author: mtwieg
author_rank: Frequent Contributor
timestamp: April 28, 2025, 03:58:51 pm
content: Unfortunately "deep cycle" has no objective meaning, either in terms of the construction of the battery or its performance. It should be seen as a marking term.Any decent battery will have specification on number of cycles, and the battery should be expected to meet those specifications. But only under the specific conditions that the manufacturer used to derive the spec (temperature, DoD, etc).The time spent in the discharged state can also matter a lot. Being left in a discharged state for long periods accelerates sulfation, which will gradually reduce the battery SoH. You can bet that during their testing, the manufacturers recharged the batteries immediately to prevent this from happening. In my experience this is the most often cause of premature battery failure. btw, for SLA batteries sulfation generally cannot be reversed (despite many claims to the contrary).I haven't personally ever seen any evidence of "memory effects" in a lead acid battery.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 28, 2025, 05:50:20 pm
content: False specs can happen, but verify first you are 110% certain you are not abusing them.Seeing that they die after winter, you suredohave temperature-compensated charge voltage curve, I'm sure you do?

author: edpalmer42
author_rank: Super Contributor
timestamp: April 28, 2025, 06:13:12 pm
content: A scooter is a really hard load for any battery due to the continuous high current involved. It likely exceeds the specs of most batteries - even deep discharge ones and will probably age the battery faster than you'd like. Maybe look for batteries that are rated for golf carts or UPS use. Note that UPS-rated batteries might not do well in high vibration environments. Check the datasheet very carefully.How smart is the charging system? Since you're pushing the battery hard, very smart, temperature-compensated charging and close monitoring by the user will be required to get maximum life out of the batteries.Has the owner considered an upgrade to LiFePO4 batteries? Some research would be required to verify this, but they might do better than lead-acid in this application.What kind of numbers are we looking at here? Volts, amps, battery models, etc.

author: brucehoult
author_rank: Super Contributor
timestamp: April 29, 2025, 03:45:28 am
content: Quote from: paulca on April 28, 2025, 02:18:59 pmTime to get rid of the lead acid batteries.LiFePO4 batteries for home battery backup now cost around US$300 to $400 per kWh but last for 3500+ cycles. They are used in BYD cars and newer models of Tesla (e.g. Model Y).Here in NZ I see an "MK" gel 12v 70AH (about 0.8 kWh) mobility scooter battery is around US$350. I see a place offering LiFePO4 replacements for $400 for 40 Ah or $700 for 75 Ah.Even if it costs a little more, the vastly higher number of cycles possible makes it well worth while.

author: paulca
author_rank: Super Contributor
timestamp: April 29, 2025, 10:33:43 am
content: I kinda 100% agree with all of you.Lithium. If it was possible I would already have swapped them for forklift LFP cells. Although that depends on "form factor" of course. The trouble is the scooter is "leased", so he doesn't own it. If he modifies it in anyway and anything breaks, they will blame the modifications and bill my friend the repair cost and probably the costs to "demodify" it.I also expect that while the batteries are, maybe, well rated down to 80/85% DoD, the specific details in the owner operating manual of how to run the scooter to that point and not beyond are too open to interruption. The operator is afforded only two indications. A "fuel guage" meter which read.... who knows what and the "battery too low" power limiter.The "fuel gauge" from what I have seen is full of all of the normal inadequacies of such a gauge, in that it dumps into the red when you move from a standing start etc. It is very likely just a compensated voltmeter.... with no scale or units.So... while a diligent and considerate user may run his batteries to 85% as the manual suggests, but he does it when the outdoor temperature is 8*C. Ends up overdoing it by 500m or so, limping home. Resulting in an actual DoD of 94% and an instant loss of 10% capacity. Repeat that little accident a few times and you have killed the battery running it hard out of spec.I think he should put pressure on the dealership/lease dealer to allow an "authorised" lithium upgrade. However I expect that would only be made available IF the manufacturer has such an upgrade kit available for that model.

author: temperance
author_rank: Super Contributor
timestamp: April 29, 2025, 11:00:26 am
content: https://batteryuniversity.com/article/bu-403-charging-lead-acidTable 2

author: paulca
author_rank: Super Contributor
timestamp: April 29, 2025, 01:56:11 pm
content: The charger is "provided" and has a custom connector utilising an XLR plug. The third pin is used for some form of communications, maybe just to detect a charger is there, maybe more.My research brought me to several options commonly used in mobility scenarios and or "light EV use", such as golf karts, factory trolleys etc. Bosch and Yuasa I took as market leading examples.The DoD vs. capacity curve for the Bosch at least show an "upward" trend in capacity over the first dozen or so cycles for all DoDs down to 100%.This I believe generates the advice to hammer the battery for the first few charges. Doesn't sound right to me, but hey. To me... if the 50% DoD always creates an upward trend in capacity, then there is no need to go to the 85%.Following this "break in" period the obvious begins to happen. the 100% Dod drops rapidly to hit 80% capacity only after <500 charges. The 85% DoD however doesn't hit 80% until 700 charges. They are claiming out to 1100 charges for 50% DoD...These sound far fetched by about a factor of 2.However. Looking closely at the datasheet for the Yuasa variants, which I have owned a small of of this range... The single line statement that will cause many many tears is this one."Storage: 3% capacity per month if not floated @20C"When I bought mine, the seller discounted it 40% because he had it in stock for 2 months. I killed it in 100 charges.ref:https://www.boschaftermarket.com/xrm/media/images/country_specific/au/parts_15/batteries_8/deep_cycle/specification_sheet_4/bosch_bg1275_battery_specification_sheet-2.pdf

author: Siwastaja
author_rank: Super Contributor
timestamp: April 29, 2025, 03:27:42 pm
content: Quote from: paulca on April 29, 2025, 01:56:11 pmSo let me guess, with no manufacturer, model number let alone spec sheet available?Crappy lead-acid chargers that destroy the batteries are common. Temperature compensation is mandatory part in real-world operating conditions, but it's easy to omit if time-to-market and lowest possible cost are more important than the fact if the product actually works or not. In such case, thechargerwould be the scam, not the battery.But hard to say without knowing what it is.

author: edpalmer42
author_rank: Super Contributor
timestamp: April 29, 2025, 05:09:13 pm
content: Quote from: Siwastaja on April 29, 2025, 03:27:42 pmAnother 'cheap charger' problem is setting the charge voltage too high. This gives them a fast recharge time - which looks good, but it cooks the battery. APC brand UPSs used to be infamous for this. I think the newer units are better.

author: mtwieg
author_rank: Frequent Contributor
timestamp: April 29, 2025, 05:14:45 pm
content: Quote from: brucehoult on April 29, 2025, 03:45:28 amI'll be all for this once lithium batteries start being recycled at rates approaching lead acid.Quote from: paulca on April 29, 2025, 10:33:43 amYeah from what I've seen lead acid batteries never get proper fuel gauges with coulomb counters. Just voltage measurement with maybe some compensation for temperature and series resistance. Usually these gauges are completely inactive when the device is powered off, so when you turn on your scooter/wheelchair, the gauge reading is total garbage for at least a few minutes.Quote from: paulca on April 29, 2025, 01:56:11 pmThat probably to account for "formatting" the battery. Some manufacturers finish formatting before sale, others want you to finish the manufacturing process for them....QuoteThis isn't unreasonable for self-discharge, but that just means you lose 3% SoC per month, not 3% SoH.Like I mention above, storing the battery for long periods at low SoC will result in loss of SoH. So in theory if you start with a fully charged battery (100% SoC and SoH) and leave it alone, it will eventually start losing SoH, but only after several months.

author: nctnico
author_rank: Super Contributor
timestamp: April 29, 2025, 05:27:33 pm
content: Quote from: Siwastaja on April 29, 2025, 03:27:42 pmYep. In the past I have built some equipment for a company which refurbishes large lead acid batteries (desulphating and so on) for electric forklifts and other traction applications. They told me they make a living because most of the lead acid battery chargers are crap. Not the batteries themselves.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 29, 2025, 05:38:56 pm
content: Quote from: nctnico on April 29, 2025, 05:27:33 pmYeah. And it isn't rocket science - just measure battery temperature, adjust charge voltage with a well-known curve. Doesn't need to be super accurate, like +/- 5degC is OK. And sensor can be inside the charger if it's located in the same environment and doesn't self-heat too much to ruin the measurement; wired sensor at the battery is of course the best. But surprisingly few are able to do this amount of engineering.

author: paulca
author_rank: Super Contributor
timestamp: April 30, 2025, 09:40:51 am
content: The emails back and forth he has had with the manufacturer reveal they use Victron blue chargers in the workshop.They also suggest that when batteries come in for service 90% of them have a dead cell and apparently the cells die in order. They replace the dead one and shift the cells around to restore the batteries. This suggests the batteries they are referring to are "modular cylindrical cells". I've never seen that before. Just plastic moulded cases.His original batteries were "Bosch", the replacements are the unbranded ones. It's possible these (and the not the originals) are the batteries from the manufacturer themselves. Maybe his problems may not reoccur... I'm skeptical though. Maybe these are "custom" batteries designed specifically for "their" scooters.The only indications we have as to how it charges is the power trace off a smart plug the charger is connected to. Can't see the actual voltage. I'm imploring him to at least run a couple of croc clips under the seal and run a datalogger on it.... at least. He is capable of doing so, but it worried about "tampering" while there is contention with the supplier.Someone mentioned vibration.My friend specifically leased a "Cross country" scooter. While not "off road" capable it is rated for gravel pathways, like country parks, coastal path, tourist walkways etc.Knowing the terrain my friend frequents... It's not exactly pleasant on an unsuspended mountain bike. It's hardpack gravel with large aggregate poking through were it's eroded and it's like that for miles at a time.If the batteries are prone to vibration the local coast path would make a very good "torture test" for them.But.... as he keeps reminding me. They say it can do it. He does it. They say it can go 30km, he goes 30km. It's a lease. If it doesn't work to spec they can either fix it or take it back. As long as he does what they say.I also think the cost of replacing batteries in the scooter so that he can continue to hammer the hell out of it will start to make it unviable to the lease company who are getting a fixed amount per month. If it starts costing them more than that replacing his batteries they will abort the lease on their side or worse start charging him to replace the batteries due to "miss use".

author: paulca
author_rank: Super Contributor
timestamp: April 30, 2025, 10:09:49 am
content: Quote from: mtwieg on April 29, 2025, 05:14:45 pmNo... it's capacity. They have a 1 month shelf-life. After that they get returned to the factory. I assume to be stripped and replated/regelled.An example of a Yuasa DC Leisure battery from the same "class".https://www.yuasa.co.uk/rec80-12.htmlhttps://www.yuasa.co.uk/yuasa/datasheet/index/sku/REC80-12I/QuoteMy rule with lead acids has always been if you want to use it, keep using it. If you store it, don't waste your time, just put it straight into the recycling and save yourself time.I have 2 exceptions. I keep 2 old starter batteries on a solar panel w/ controller. These batteries are too far gone to trust, they have had their life. However, I know that when fully charged either will start my car. The large marine battery has a handle and goes in the boot/trunk if I'm really worried about getting stranded (usually winter after the car has sat up for a few weeks unused).I also know in a power cut the marine battery will run LED lights and mild electronics for hours. Even though when new it would run them for a day.

author: mtwieg
author_rank: Frequent Contributor
timestamp: April 30, 2025, 02:08:41 pm
content: Quote from: paulca on April 30, 2025, 10:09:49 amI would never interpret this wording to mean it loses 3% SoH per month. That is certainly not normal for any PbA battery I've ever seen.QuoteSoH loss over time can't be worse during storage than during use, so long as it's not stored with low SoC or at extreme temperatures.

author: thm_w
author_rank: Super Contributor
timestamp: April 30, 2025, 10:18:01 pm
content: As you say we don't know if the scooter actually cuts off at 85% DOD. 11V is 100%+ DOD at very low current. If you knew what the motor current was you could maybe inline a low voltage cutoff relay, with the risk that you get stuck without power.Leasing a scooter sounds like a terrible idea. I'm sure you can find used units that would work once the batteries are replaced for less than a years worth of lease payments. But if the scooter stopped working with the Lifepo4 batteries in place, the solution is simple, keep the lead acid batteries on hand and swap them back in before taking for service.I have a Panasonic battery here that is ~10 years old, never been used, and still has 11.80V on it, though its some special model:https://www.tme.eu/Document/b212890db0910164af9e90fe38847021/LC-P1238.pdfIt still had 25Ah, so at least 66% of original capacity (can't recall the discharge current though, I'll maybe try it again).