Battery under test

 
 
 
 
 
 
Eat's Sleep's craic
Avatar
Gender:
Location: Galway
Age: 47
Posts: 2035
Registered: 07 / 2017
My Motorhome:
Base Vehicle: Vauxhall Movano 2.5 CDTI
Subject:

Battery under test

 · 
Posted: 15.02.2021  ·  #1
Well I have had a couple of productive days getting some re-wiring done on the van’s habitation electrics. I have re-housed various relays and switches into a new ABS enclosure and built in a new ground plane and busbars and finally got around to cable numbering everything.

While this was all going on, I have had the battery disconnected. It is the Halfords HLB 618, 115 Ah rated. It’s about 3 years old and I think might be on the way out. I want to try measure it’s capacity. It was fully charged when disconnected. When I reconnected it this evening, the battery was reading 12.8 V. I have put it under soak test since about 16:30 this afternoon by powering a cooler box, which draws close to 4 amps., and I have since turned on some LED lighting. I checked up about an hour ago. The voltage under load has now dipped below 12 V. My battery monitor tells me the battery has depleted to 82% state of charge.

The plan is to check it again before calling it a night, recording the S.O.C, disconnecting the load and battery, letting it sit overnight and checking the voltage in the morning. I want to compare what my monitor assumes is the S.O.C to what the rested voltage says.

 


I wonder how low the voltage should dip under load for this long? I should have done this test when the battery was new, just to have something to compare.

Liked by: baguette

Eat's Sleep's craic
Avatar
Gender:
Location: Galway
Age: 47
Posts: 2035
Registered: 07 / 2017
My Motorhome:
Base Vehicle: Vauxhall Movano 2.5 CDTI
Subject:

Re: Battery under test

 · 
Posted: 16.02.2021  ·  #2
 


So I finished up last night with the battery run down to 69% Soc. That’s according to my monitor which assumes the battery capacity is as new, 115 Ah. But that is what I want to measure as I suspected the capacity has degraded. The only thing I can be sure of is that I pulled 33 Ah out of it over the course of load testing. The battery monitor doesn’t need any guess work to report that.

With the battery left in open circuit overnight, the 12 hour resting voltage = 12.55 V. That’s higher than I expected. Many charts might estimate the battery at about 90% Soc with that voltage. So without the manufacturers data sheet, that voltage is meaningless to me other than to suggest that it has a higher rated cell voltage than most other wet cell batteries on the market. It might also suggest the battery capacity has not really degraded after all.

I have since plugged in a mains charger and it reports to me that the battery Soc is 70%. I now believe the rated capacity has not degraded. I also reckon my mains charger is quite accurate in determining Soc , whatever algorithm it is using. I fully expected the capacity to be down and that I would be reprogramming the monitor to account for a lower Ah reference. This is good news of coarse but I can no longer justify buying a new pair of batteries. Not this year anyway.


Eat's Sleep's craic
Avatar
Gender:
Location: Wexford
Age: 54
Posts: 3776
Registered: 02 / 2017
My Motorhome: Bailey autograph 730
Base Vehicle: Peugeot 2.2 130 Hp
Subject:

Re: Battery under test

 · 
Posted: 16.02.2021  ·  #3
Have you no proper work to do 😆😆
Ain’t it amazing how we can find ways to amuse ourselves. 👍


Eat's Sleep's craic
Avatar
Gender:
Location: Galway
Age: 47
Posts: 2035
Registered: 07 / 2017
My Motorhome:
Base Vehicle: Vauxhall Movano 2.5 CDTI
Subject:

Re: Battery under test

 · 
Posted: 16.02.2021  ·  #4
Quote by Daffysparks

Have you no proper work to do 😆😆
Ain’t it amazing how we can find ways to amuse ourselves. 👍


Would you stop. Beating the lockdown blues eh? 😂

Liked by: Daffysparks

Eat's Sleep's craic
Avatar
Gender:
Location: Wexford
Age: 54
Posts: 3776
Registered: 02 / 2017
My Motorhome: Bailey autograph 730
Base Vehicle: Peugeot 2.2 130 Hp
Subject:

Re: Battery under test

 · 
Posted: 16.02.2021  ·  #5
There is always something to be at in a more mature van, that is for sure....... whether it’s necessary or not. It keeps us busy


Selected quotes for multi-quoting:   0

Registered users in this topic

Currently no registered users in this section

The statistic shows who was online during the last 5 minutes. Updated every 90 seconds.