Advertisement
Message Forums |
|
 Topic: Issue with leisure battery and coolbox
|
Page: 1 2
  |
13/11/2017 at 1:37pm
Location: None Entered
Outfit: None Entered
View Profile
Reply
Quote
|
Joined: 20/8/2017 Standard Member
Forum Posts: 14
| Site Reviews Total: | 0 |
|
| Site Reviews 2024: | 0  |
| Site Reviews 2023: | 0 |
| Site Reviews 2022: | 0 |
| Site Reviews 2021: | 0 |
| Site Reviews 2020: | 0 |
| Site Reviews 2019: | 0 |
| Site Reviews 2018: | 0 |
|
| Site Nights 2024: | 0 |
| Site Nights 2023: | 0 |
| Site Nights 2022: | 0 |
| Site Nights 2021: | 0 |
| Site Nights 2020: | 0 |
| Site Nights 2019: | 0 |
| Site Nights 2018: | 0 |
|
Quote: Originally posted by Grampian91 on 11/11/2017
Quote: Originally posted by achrn on 07/11/2017
How are you measuring battery voltage?
If you're doing it with the fridge connected, the voltage reading will be more a function of the instantaneous current draw than of the state of charge of the battery.
That is, while it is (broadly) true that you can gauge the state of charge of a lead-acid cell by measuring voltage, that's only when the battery is open-circuit (ie nothing connected, no current draw). You need to disconnect the fridge, let the cell voltage stabilise, then measure the voltage.
Wrong.
Testing a battery off load can give a totally false figure for its state of charge.
A duff battery can read 12.6v+ and yet when put under any load even 1 or 2 amps the voltage could plummet to below 11 volts.
You're talking about something different.
Specifically, you are apparently discussing a battery with a very high internal resistance (though other faults may give similar effect), which is itself a fault, but one that's not related to state of charge.
If you want to determine state-of-charge of a lead-acid battery, an open-circuit voltage is a reasonable way to do it, and a voltage test of the battery under load is most definitely not the way to do it, because (as I said) that reading will be more a function of teh current than about state-of-charge. However, state-of-charge doesn't tell you that everything is 100% tickety-boo with the battery (and I never claimed it did).
If you have your battery under load and change the load so the current reduces, the voltage will rise. If this voltage actually was proportional to state of charge, it would mean the battery has become more charged without putting any charge in (indeed, while continuing to draw charge out).
In your anecdote, it simply means the battery was near fully charged, but ALSO (in your terminology) 'duff'. I haven't said open-circuit voltage tells you anything about 'duff'iness. It does however tell you state of charge (approximately).
If you want to determine state of charge by means of voltage, the correct way to do it is with no current drawn.
|
14/11/2017 at 1:51pm
Location: None Entered
Outfit: None Entered
View Profile
Reply
Quote
|
Joined: 20/8/2017 Standard Member
Forum Posts: 14
| Site Reviews Total: | 0 |
|
| Site Reviews 2024: | 0 |
| Site Reviews 2023: | 0 |
| Site Reviews 2022: | 0 |
| Site Reviews 2021: | 0 |
| Site Reviews 2020: | 0 |
| Site Reviews 2019: | 0 |
| Site Reviews 2018: | 0 |
|
| Site Nights 2024: | 0 |
| Site Nights 2023: | 0 |
| Site Nights 2022: | 0 |
| Site Nights 2021: | 0 |
| Site Nights 2020: | 0 |
| Site Nights 2019: | 0 |
| Site Nights 2018: | 0 |
|
Quote: Originally posted by Grampian91 on 13/11/2017
So your off load test shows a large 110 battery at 12.68 volts, would you say it was well charged?
Generally yes.
Quote:
Why then will the battery only light a 20w bulb for less than 30 seconds before it dims to a glow worm?
Because it's faulty. It may be fully charged, but faulty (internal corrosion, sulfation, bad connection, etc etc).
Saying that a battery is fully charged is not at all the same as saying that it's in good condition, has low internal resistance, or is capable of providing a particular current for a particular duration.
I haven't claimed that open circuit voltage tells you that the battery is fully operational, 100% fine, good for any and all purposes, or that it has a high capacity. I've said it tells more about state of charge than does measuring the voltage under load.
|
|
|
6566 Visitors online !
Free UKCampsite.co.uk Window Sticker - Recommend to Friend - Add a Missing Campsite
[Message Forums]
[Caravan Sites & Camping]
[Company Listings]
[Features / Advice]
[Virtual Brochure]
[Shop!]
[Reception]
[Competitions]
[Caravans & Motorhomes For Sale]
[Event Diary]
[Contact Us]
[Tent Reviews]
Please note we are not responsible for the content of external sites & any reviews represent the author's personal view only. Please report any error here. You may view our privacy and cookie policy and terms and conditions here. All copyrights & other intellectual property rights in the design and content of this web site are reserved to the UKCampsite.co.uk © 1999 - 2024 |
Advertisement
|
|
|
