Float comes on at different charge levels when using generator

[Mjkohler]

Hi my name is Melinda and I am pretty solar naive. (in fact I am sure my installer was grumbling something about some people shouldn't have solar installations about myself when He was muttering).

So here is my situation.
Sun and Summer batteries are charging fine. Rainy days one after the other (and we seem to be having a lot of them), not so good.

So I haul out the generator. Good solid generator, well capable of doing the job. First day it's used get batteries up to 100 with no problem. Second day might only reach low nineties. Third day mid eighties by the fourth day I'm praying for some sunshine.

At the most my power usage for any 24 hour period is about 12 percent. But when you have Grey skies that 12 percent adds up quickly.

Generator has been serviced recently, inverter is fairly new and batteries should not need replacing as yet.

Why does my generator, if used over several days in a row, go to a lower float rate each day? Batteries are the enclosed type that don't need checking.

Thanks for any ideas you can give me.

[Bala]

OK, need to clarify some terminology.

Percentage. This should be a % of State of Charge. Soc.

Float Rate. Float is a Voltage setting along with Bulk and absorb.

It seems you are running your generator when there is not enough sun and it is not able to get your Soc back to 100% every day?

If so then your batteries may be unhealthy. The generator/charger may not be big enough. You may not be running the generator long enough.

[Ampster]

Assuming the batteries are some form of Lead Acid, they will do better with a good Absorb time to keep them topped off. A Float setting at the correct voltage can also do that.
THe key is the voltage value for those parameters. Float and Absorb are just variations in Constant Voltage stages of charging.

[Mjkohler]

Thank you both for your replies to my query.
It is going on winter here in N. Z. and the generator will be used at times.

The generator is a good size and ample big enough for the job. And I have had it run for hours at a time. But once it is on float the SOC will remain the same no matter how long the generator runs.

I agree full heartedly that a good Absorb time or a float setting at the correct voltage is the key. (though why the SOC is not stable each day is a head scratcher).

How do I determine?
1. A good absorb time
2. The voltage value for float? And absorption?

I run a
Victron Energy Multi plus charger/inverter 3000
MPPT Solar Charge Controller eTracer
Battery Monitor TM 2005 RV
2 x Vision 6FM230X 12V 230 AH batteries, valve regulated, rechargeable, constant voltage charge
Cycle use 14.4 - 14.7
Standby use 13.2-13.8v
Initial current less than 69A

Your help is greatfully received.
Thanking you

[Mjkohler]

I put my generator on about 30 mins ago. The SOC of batteries showed 74. Just checked battery monitor and inverter/charger. Monitor shows SOC 79. Inverter/charger is on float.

[Bala]

I have similar batteries but 2v each and a 24v system.

The specs for mine give a V at which point the batteries will gas. My settings are just below that point.

See if you can find a V point for gassing for yours and if you can adjust the charger to stay at that V.

[Bala]

Having a look at the specs for your items.

If I have the correct items the batteries have a maximum cycle V of 2.35 V per cell so 14.1V for a 12V battery.

Check your manual for the charger but what I see is the standard setting for absorb is 14.4V. That may not be good.

Also make sure there is no equalize set.

There also appears to be a setting for Absorb repeat, standard at 7 days. This may be why you have a good charge on the first day but not repat days.

Im in Qld Australia. I have been to NZ a couple of times caving and Kayakaing.

[Mjkohler]

Thank you Bala. I have no idea what your first post referred to sorry, as I am technically naive. V point and gassing?

I will find a manual and see if it gives me instructions for reading settings.

The idea for checking out absorb repeat sounds good.

Why is 14.4V for absorb possibly not good? Too high?

Luckily sun is helping out generator a little today.

I have been in Queensland recently to visit my brother in Bundaberg.

I'm in Golden Bay which is good Caving and Kayaking territory.

[Bala]

V us voltage. When batteries are charging there is a certain V at which they will start to bubble and gas. As you cannot replace electrolyte in sealed batteries you do not want them to gas. As the spec sheet I found for your batteries lists 14.1V maximum charging I suspect V over that will cause excessive gassing.

Look to see if you can change V settings on your controller. You could look to set bulk absorb and float to 14.1 in winter especially.

I live near mission Beach. I have a friend who is a doctor who lives in Motueka. I caved Takaka and Ellis Basin.

[Mjkohler]

Thank you so much. I'm in Takaka. Small world.