Car battery datasheet needed - Page 1
Forum section: electronics / projects

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: February 22, 2018, 06:50:20 pm
content: I can't seem to find the datasheet of this old car battery.I'd like to use it on a UPS and would like to know if the charge/discharge characteristics are in line with what the UPS can provide.If anyone can help me find it I would be very grateful thanks!

author: Benta
author_rank: Super Contributor
timestamp: February 22, 2018, 07:24:53 pm
content: Can't help with a data sheet, but car batteries are not really suitable for UPS use.They are designed for delivering high cranking amps, but more importantly, they don't like deep discharge. You should avoid going below ~80%, which is not what you want for a UPS.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: February 22, 2018, 07:26:34 pm
content: I am well aware of that but I have no other use for it so might as well kill it that way...

author: drussell
author_rank: Super Contributor
timestamp: February 22, 2018, 09:20:34 pm
content: Quote from: Benta on February 22, 2018, 07:24:53 pmWhaaaa?!Where are you using your UPS?Most UPS use is to provide very infrequent backup power for short periods of time during a supply interruption. This is very similar to the use of starting a typical automobile engine. Most of the time you use just use little more than the surface charge for a moment or two, rarely discharging the cells more than a few percent to ride you through a short interruption in mains power.Most UPS installations do not often require repeated long-term, deep-cycle discharges. The few times where you actually have an extended outage, a typical automotive starting battery is certainly sufficient for doing the odd full cycle here or there, though it significantly reduces the total lifespan if you do that more than a few times. As long as you only do it a few times in the lifespan, it is totally fine.REPEATEDdeep cycling is a completely different story (off-grid solar etc.)I very often use cheap starting batteries for my UPS systems! You just need to look at the "reserve capacity" spec more than anything else. The servers here in my basement usually have a 2 x 2 series / parallel (it is a 24v UPS) set of cheap 120 minute "reserve capacity" starting batteries connected to them which generally last about 4-6 years or more in constant "float" mode, even from the typical over-volted APC charging circuit. As long as you buy the ones that you can replenish the water in the electrolyte on, you should be good to go for many years.Different battery styles are built with different chemistries and physically different plates. A starting battery will have more, thinner plates to provide higher instantaneous cranking power. A "deep cycle" battery intended for repetitive use will have fewer, but thicker plates, thus a lower "cranking amps" spec, but better total long-term capacity and cycle life.The last set that I rotated out from the office were only ever used a few times for < 10 minute outages and two deep discharges during prolonged outages (one being a scheduled outage from the power company, in our case requiring me to bring in a backup generator overnight, just sat it in the reception area with an exhaust out the window... lol)Spending the extra dough on a set of deep cycle batteries for that usage would have cost 4-5x as much and in the end, they would have only lasted 0.00% longer in service life.Unless you need constant cycling, a good quality starting battery is actually the proper fit for most typical UPS usage (charge/discharge) profiles!

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: February 22, 2018, 09:26:48 pm
content: Quote from: drussell on February 22, 2018, 09:20:34 pmLike I said, I am only using this battery and not a deep cycle one because I already have it laying around from an old car that I have put a new battery in so will keep using it until it no longer meets my power requirements.It lasts 55 minutes at a constant 400W draw so more than enough for my need at the moment. When it fails to stay on for at least 15 minutes I will throw it away and get a deep cycle battery instead!

author: Gyro
author_rank: Super Contributor
timestamp: February 22, 2018, 09:35:21 pm
content: Quote from: drussell on February 22, 2018, 09:20:34 pmJust a reminder that if the charge is "over-volted" and you're needing to add water, then Hydrogen gas is being evolved.

author: drussell
author_rank: Super Contributor
timestamp: February 22, 2018, 09:46:34 pm
content: Quote from: Gyro on February 22, 2018, 09:35:21 pmAbsolutely. Even though this kind of gassing is over a very long period of time,anytime you are not using sealed / self-gas-absorbing style batteries youmustconsider your installation for adequate venting, etc!For any kind of large installation, I recommend battery box for your array, properly plumbed to fresh air with a vent off the top and an intake near the bottom. You also should construct it in such a way that it will contain any acid spilled/expelled for any reason, etc. by either containing it in a sealed tray or having enough base (even just a bunch of baking soda) in the bottom of your box to neutralize any excess. Proper DC-rated current interrupting devices are also a must-have on larger arrays!

author: drussell
author_rank: Super Contributor
timestamp: February 22, 2018, 10:02:53 pm
content: Quote from: drummerdimitri on February 22, 2018, 09:26:48 pmFor maximum lifespan you will need to check the float voltage on your UPS's charger. If it is adjustable, it is often advantageous from a battery-longevity standpoint to lower it a fraction of a volt but this depends on the exact type of cell, the actual physical cell construction and additives to the lead comprising the plates (calcium on the maintenance free ones, antimony, etc.)The best way to test it out, if you can actually readily adjust it (instead of just having to live with it or modify resistor values, etc.) is to let it charge all the way up to full float level for a day or two and then measure the standing charging current. If it is more than part of an ampere on a typical, properly working, non-self-hyper-discharging car battery, you're probably floating at a slightly elevated voltage from optimum...I usually use and sell Interstate Batteries but I can't find a link to the charging guideline .PDF at the moment, but here is a similar charging guide from Exide:http://www2.exide.com/Media/files/Location%20Data/Battery%20Charging%20%26%20Storage%20Specs%20%2011_13_15.pdfEssentially, I would usually prefer to have my chargers set to float at 13.2-13.5 rather than 13.8-14.1 like you often see...

author: Benta
author_rank: Super Contributor
timestamp: February 22, 2018, 10:24:54 pm
content: Quote from: drummerdimitri on February 22, 2018, 07:26:34 pmSo why the **** are you asking for a data sheet? Just use the battery, period.

author: drussell
author_rank: Super Contributor
timestamp: February 22, 2018, 10:45:18 pm
content: Quote from: Benta on February 22, 2018, 10:24:54 pmPresumably, he was just looking for a charge profile and to know if it was going to somehow kill the battery excessively quickly or overtax his UPS's charger or something.The answer is, of course, no... It should work just fine in this configuration.Connect it up with some appropriate cabling of sufficient size (keep them short and beefy, typically 8-10ga on a small UPS, so it is well connected with little voltage drop) and enjoy your new, extended run-time on your next power outage.