Hi All,
I posted the other day about my off-grid system losing voltage. I have a (now aging) off-grid system that comprises of 24 lead-acid batteries, a solar system and backup generator.
Over the last couple of weeks it’s not beenkeeping it’s charge at 48V for more than 3-4 hours. Usually after the generator has kicked in to charge and do a full float, it’s lasted overnight easily. The length of time it keeps the charge is decreasing rapidly.
I am not an expert on this as I inherited the system when I bought the place and the installers (Off-Grid Energy) don’t seem to exist. I know in the past one of the cells was replaced but I am at a loss as to how to source one or replace one safely. It’s not my skillset.
IS there anyone in an around the Peak District that could offer any help please?
Not only is it my only source of power but in the spring and summer months I let the place out and it is a significant part of my income.
Any help will be very much appreciated.
*Just to note, I am in the process of finding installers to upgrade all of it including the batteries, but this may be a number of weeks.
Thanks, Paul. A bit desperate and slightly panicky!
HI Ludo, thanks for this. Yeah I did wonder as to whether it would be one cell. Again, excuse my naiivity but what would cause a short circuit. There’s nothing around the batteries or touching them, or do you mean there could be something inside one of them? (I have been very careful when I have topped them up).
As for the hidden load - again, good point. But would that not show up as a “load” or consumption?
All seems fine for a few hours and then the voltage drops off a cliff.
I will tke your advice and see if I can find anything.
As batteries age they shed material from the plates and the plates can warp both causing a short inside one cell. This cell will then often be warmer than the other ones. If you disconnect cells then you will find one with a lower voltage.
While I can not make a direct recommendation, Ed Shiers on Four Counties Marine works in that area doing canal boats, he knows Victron and canal boats are by definition off grid. Just google Four Counties Marine. He may know someone.
You probably have a system with 24 lead-acid CELLs. A battery is defined as a combination (mostly in a row) of single cells.
When you have access to the single cells, you can easily check their individual voltages. The reason for a shorted cell can be:
Faulty separators.
Lead particles or other metals forming a circuit between the positive and negative plates.
Buckling of the plates or.
Excessive sediments in the bottom of the jar.
My lead acid lasted for almost 20 years but they had an easy life.
Make sure each battery has liquid.
Check each cell for voltage with a multimeter. If you dont own one, buy one. They’re cheap.
Check voltage in the evening when the voltage drops. Each cell should be about 2.1V.
Check and clean each terminal. Take them apart
and tighten them up. This will help a lot. Turn the system off to do this.
Because they’re old can always change out a single one to get you through.
A tablespon of caustic soda in each cells give them a boost too. I’ve been offgrid for 25 years and it works.
Hi, thank you very much for this. I have tested all 24 of the cells in terms of volatge and they are all around 2v with the exeption of one, which is about 1.89
I have religiously kept the batteries topped up with de-iosnied water (as did the bloke who had it the place before.)
Never thought about the acidity of them though - in another post someone did show me a table of specific gravity at various temperatures. In terms of caustic soda - there’a many products that have it such as cleaning products but I suspect they also have lots of other stuff in them that may contaminate the cells.
Would something like this (Sodium Hydrox) be suitable or should I try and find weapon - grade stuff?
Hi Tom, are you well? Hope so. Thanks for this. Steep learning curve for me but this all makes sense. And yes, I should have said “cells” not batteries. All of what you said could be possible given the age of them. I have been very careful looking after them and keeping them topped up with de-ionised water but as you say, sediment or other contaminents could be at play here.
I have tested all the cells (once I was told there was a little port on each terminal for a tester!) and all seem ok barr one, which is at 1.9 whereas the rest are around 2.1.
I think my mission has changed from having all the system replaced (which was for convenience’s sake whilst the old system was still in place) to an initial stage of replacing these lead-acid cells asap and moving the system at a later date.
My challenge still remains in finding someone to do it as as the few I have spoken to over the last 48 hours seem to not have the willingness of skillset to do anything other than fit an entire new solar-based system from scratch. With all due respect, it seems like a lot of “solar energy” firms are good at what they do as long as it doesn’t stray from the Meccano-style kit.
Thanks for your help and advice and I will persevere.
Not sure if your inverter is a 24v/48v but you could turn your batteries into 24v.
I had a overnight failure of 1 battery and managed to buy a 2nd hand one from a scrap dealer to tide me over for 2 months. I had to drive 800km return but it gave breathing space until i came up with a fix.
Once the batteries are that far gone you may as well abuse them.
I now have a lithium build set…
Many dealers don’t want to instal into an existing system. Mainly to do with money. Others only instal, and have little knowledge.
@PaulF
Cold Pb batteries can lose a lot of capacity. And sag much more in V under load. Maybe they could use a good stir-up with an Equalize?
If you actually lose a single cell you could change to 46V. Settings adjusted to suit.
But don’t do that caustic soda thing, please. Guaranteed to warm them and stir them, but highly dangerous.
