Cheap VRLA battery leak risk / replacement - Page 1
Forum section: electronics / general

author: bd139
author_rank: Super Contributor
timestamp: June 17, 2019, 04:49:22 pm
content: Need to replace a duff 2.9Ah 12V VRLA battery in my alarm. The original powersonic part is completely unobtainable in the UK due to shipping restrictions (typical!) therefore I'm thinking of sticking in a no brand RS Pro one in the unit which is same dimensions and capacity. Both are AGM subtype batteries.Is anyone aware of any leak risks with these running on their side?I am basically worried now I cracked it open for the first time as the idiots who designed the alarm put the battery at the top, cable tied to the top of the unit on its side so if it does leak it'll piss acid all over the board, ruin it and cost me a new alarm. There isn't enough room to mount another one upright in it.

author: james_s
author_rank: Super Contributor
timestamp: June 17, 2019, 05:21:48 pm
content: I don't think I've ever seen one leak. Read the datasheet but most are specifically made to be used in any position.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: June 17, 2019, 05:34:12 pm
content: I'm using those types already for a while and never had any issues; I consider them much safer in handling than any liquid acid type

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 17, 2019, 11:00:43 pm
content: Replace it with a 3S lithium pack with a balancing BMS along with a Schottky diode and 12V LDO to limit charge voltage to 4V/cell with minimal interference to the battery powering the circuit?

author: james_s
author_rank: Super Contributor
timestamp: June 18, 2019, 12:21:49 am
content: I would not recommend messing with lithium ion unless you know what you're doing. They have excellent energy density but they are much more fickle than lead acid and they are prone to catching fire if abused.Now there are protection boards and charging ICs now that make working with them much easier than it used to be but it's still not something I'd recommend to the novice.

author: Gregg
author_rank: Super Contributor
timestamp: June 18, 2019, 03:35:17 am
content: VRLA batteries are quite rugged and very forgiving. If you are concerned about leakage, try to find a plastic container that will fit the location and put some washing soda in the bottom covered with some cotton or wool cloth. The cloth helps keep things in check from fizzing if a leak does occur. VRLA batteries usually don't have nearly the amount of electrolyte as flooded LA batteries and if they do leak it usually is a very slow leak.If you are interested in crappy VRLA batteries made to be installed on their sides; enclosed are some pictures of several strings of 1430 AH VRLA cells on the 11th floor of a high rise building in earthquake zoned Silicone Valley; note the steel support beams. The older cells (brown covers) are over 50% cracked and I had just taken them off line before they became a real problem. A year before the battery manufacturer sent a crew to replace all of the valves under warranty; a lot of good that did. Part of the problem is tha room was quite hot and the battery strings placed too close for air circulation.

author: bd139
author_rank: Super Contributor
timestamp: June 18, 2019, 07:30:08 am
content: Thanks for the replies everyone. Much appreciated.I’ve decided to replace it with a Yuasa 2.3Ah unit which is the same size and not worry about it. Based on the comments above the cells seem pretty robust unless abused and this thing is ticking over doing not a lot.As for lithium ion, I’ll pass on that. I’ve built packs with the BMS boards from China a couple of times from recycled NOS thinkpad packs so aware of the process, risks etc but the things aren’t really suitable for this on a cost basis when the right SLA is £15 including delivery and doesn’t require making anything.The only thing I will probably do here is replace the charger in the unit which is basically a transformer, one diode, two resistors, a zener and a capacitor. The resistor which was loading up the zener has overheated to the point the stripes have worn off