100Ah 12v Battery voltage under load


Ian

Administrator
Joined
Feb 23, 2002
Messages
19,574
Reaction score
1,297
Bit of a random question... but maybe someone here will know!

I've got a 100Ah deep cycle gel leisure battery which is hooked up to a 3000W inverter (not using it near full capacity). I'm measuring the current voltage across a shunt and displaying the results on a meter, which should give me a better idea of the in-use battery condition, rather than a simple voltmeter that would only give an accurate reading when there is no load.

When I'm using a large load (i.e. 1000W, about the max I'd use), the voltage drops to about 11.6v in use. My cabling is 35mm so I don't think that's the issue here as it can handle high current just fine. Can anyone advise on what is the lowest voltage drop I could allow without damaging this sort of battery? I know that I can't let this voltage drop to below ~12.2v when there's no load, but it's the high load voltage I'm interested in.

I've had a good search and read up, but I get a lot of different results. Most focus on the 12.1-12.2v max discharge voltage, rather than the drop during load. Those that mention it don't give much of a guide. Hoping someone here has experience!
 
Ad

Advertisements

muckshifter

I'm not weird, I'm a limited edition.
Moderator
Joined
Mar 5, 2002
Messages
25,600
Reaction score
1,104
In the Marine World a drop to 11.6 could be interpreted as a damaged battery.

 

Ian

Administrator
Joined
Feb 23, 2002
Messages
19,574
Reaction score
1,297
Cheers @muckshifter, that's one of the pages I was reading. From what I now understand, as long as the battery doesn't drift too far away from 12V whilst under heavy load, I should be OK - as it's not going to damage the battery chemistry. If it's at resting voltage, I should try and keep it about 12.2v on my particular battery.
 

crazylegs

Member Extraordinaire
Joined
Dec 31, 2004
Messages
5,719
Reaction score
54
Cheers @muckshifter, that's one of the pages I was reading. From what I now understand, as long as the battery doesn't drift too far away from 12V whilst under heavy load, I should be OK - as it's not going to damage the battery chemistry. If it's at resting voltage, I should try and keep it about 12.2v on my particular battery.
So does that mean your battery is shot Ian, how old is the Battery?
Is this a campervan setup?
 

Ian

Administrator
Joined
Feb 23, 2002
Messages
19,574
Reaction score
1,297
The battery is brand new and OK, I'm just not sure how hard I should be pushing it. I heard back from the retailer today and they sent me a handy discharge graph which shows how hard I can expect to push it. I've been really impressed with their tech support. Here's the graph in case it's any use to anyone in future (attached).

They suggested I limit to 25A discharge if I want the battery to last a long time, which is OK by me - it won't often be used with the inverter for heavy loads. I'm mainly using it as a battery backup in my workshop and because I sometimes need to use powertools for jobs on the road and don't have power nearby. I'll likely also use it to power my telescope from a 12v socket :D.

s-l1600.jpg
 
Ad

Advertisements

crazylegs

Member Extraordinaire
Joined
Dec 31, 2004
Messages
5,719
Reaction score
54
Ahhh gotcha

I take it you know not to discharge below 50% charge in AGM cells for the longevity of the battery, looks like your just going to be within parameters.
 
Ad

Advertisements

Ian

Administrator
Joined
Feb 23, 2002
Messages
19,574
Reaction score
1,297
Cheers @crazylegs, yeah I want to try and keep the battery in good condition for a long time, so will avoid discharging it past 50% :D.
 

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.

Ask a Question

Top