Can I damage a panel by using two different batteries that one has a more higher amp rating than another one?

Probably not, but you can damage the batteries.

How so? what kind of stuff can happen? I want to know before I do anything stupid.

Well, being that they’d be charged at the same time, one could get over/undercharged.
That’s bad.
In some battery types (Lithium, though those are rarely if ever used in fire alarm systems), they can actually fail and eventually explode.

Oh well :slight_smile: thanks for the good advice, if it wasn’t for you i could have died 5/5

Don’t quote me on this but I think it theoretically would work, but I wouldn’t attempt it. Lead acid batteries have a highly corrosive acid in them that can hurt you pretty bad.

Also what would happen if I power the panel with batteries that are a lower amp rating than required?

When you say “amp rating,” are you referring to the max draw or the amp hours?

The batteries I might think of using are 12 volts 2Ah, Yes; I would assume map hours or whatever.

Most panels wouldn’t have a problem with it because their charging circuits sense when the batteries are full. It does this by sensing the amount of voltage in the batteries. As long as they are both 12V batteries, you shouldn’t have a problem.

So If I use one battery thats discharged and one full battery will there be a trouble in the panel? I just got 2 12V 7Ah batteries and one is coming in at 0.02VDC and another at 12.3VDC. Will the panel charge them and will there be trouble? Also if a NAC shorts while the panel isn’t in alarm can that break anything? Jw.

Probably not, but that is terrible for the batteries. You should safely discharge (Google it) both batteries, and then charge them together, as long as they have the same voltage and amp hour rating.
Don’t quote me on this one, but this is something that applies to a different kind of battery, and I assume this one as well: a 12v battery should never be putting out that little voltage.


Thanks for the information, Prog and others!

Batteries wired in series electrically operate as one battery, as the end cell of one battery is joined to the end cell of another via the series wire between the batteries.

It’s not the best to connect a discharged battery to a charged battery in series and attempt to charge it in a set. This could cook the good battery because the discharged battery will draw a very high charging current that must pass through the good battery.

Batteries in series should (shall per code) be from the same manufacturing lot, and should have the same state of charge when they’re installed. For us, batteries come in cases of 8-10 so that’s typically never a problem. This way, that battery set is always charged and discharged at the same time with the same current (series circuits, current is the same at all points). 80% of the time, these batteries will also fail at the same time. Now, if you mix, say a Werker from 2010 with an Ultratech from 2009, you have two batteries that have different chemical compositions. It won’t cause any noticable harm, but one could have a higher sulfation buildup than the other, etc. Not a big deal for the applications of the panels on this site, but I’d replace them on a service call.

Personally, I would get that dead battery charged before putting it in the panel. If it’s less than 1 VDC you have some serious trouble, it’s very, very, very bad for a battery to be that low (it can damage the lead plates by a sulfation buildup, that reduces the battery’s current). I carry a 500 mA trickle charger that I got from a local battery shop. It’s great for that kind of thing and only cost about $20. Also, if it’s been sitting that low for more than a few days, irreversible battery damage could have already been done. These alarm batteries are cheap, I won’t lie. I see some fail, crack, leak, etc sometimes 2-3 years after installing, they all bear that same sentence on them, “made in China”.

I live not far from the Yuasa battery plant in Reading, PA. I’ve seen those Yuasa batteries go 10 years and still pass load testing. No lie, I’ve seen Yuasa batteries split and crack open and they still pass load testing. Off topic, but domestic manufacturing quality shows.

Good insight! Thanks!