Driver
Member
There seem to be many types of battery testers, but I cannot find any that actually measure capacity. Do they exist? I am trying to avoid the hassle of strings of headlamp bulbs, stopwatch in hand, etc.
Measuring battery capacity.
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Hurricane
Well-known member
As far as I know, something to measure the actual capacity of a battery doesn't exist.
I think the best way is to incorporate a battery monitor that takes into account more than just the voltage.
These monitors store the current flow (in both directions) and display a better indication of the battery condition.
Most of these battery monitors incorporate a well known law called Peukert's law.
I'm no expert but I understand that Peukert's formula takes into consideration the age/use of the battery.
So my above comment is no use to you if you don't have a battery monitor fitted.
The best way that I have found to test a battery is to attach one of these:-
If the battery voltage stays good after 10 seconds with the test switch on, the battery is good enough to use.
If not, I would change the battery.
There are more modern testers that are supposed to check the battery using a device similar to a multimeter but I don't understand how they work so I stick to the good old technique of "hitting it" with a big load and measuring how it responds.
If you haven't got a battery monitor, I suggest that you fit one when you next change the batteries.
You can then monitor the percentage capacity of the battery from a simple remote gauge (or an app on your phone).
I think the best way is to incorporate a battery monitor that takes into account more than just the voltage.
These monitors store the current flow (in both directions) and display a better indication of the battery condition.
Most of these battery monitors incorporate a well known law called Peukert's law.
I'm no expert but I understand that Peukert's formula takes into consideration the age/use of the battery.
So my above comment is no use to you if you don't have a battery monitor fitted.
The best way that I have found to test a battery is to attach one of these:-
If the battery voltage stays good after 10 seconds with the test switch on, the battery is good enough to use.
If not, I would change the battery.
There are more modern testers that are supposed to check the battery using a device similar to a multimeter but I don't understand how they work so I stick to the good old technique of "hitting it" with a big load and measuring how it responds.
If you haven't got a battery monitor, I suggest that you fit one when you next change the batteries.
You can then monitor the percentage capacity of the battery from a simple remote gauge (or an app on your phone).
Refueler
Well-known member
Capacity is not measurable static as its a function of load vs time.
Therefore measuring how long and at what amps it takes for battery to reach a set level of voltage is basically the only way. Even fancy meters base their readings on load discharging and then rate / time to recharge.
Therefore measuring how long and at what amps it takes for battery to reach a set level of voltage is basically the only way. Even fancy meters base their readings on load discharging and then rate / time to recharge.
wonkywinch
Well-known member
This device claims to measure actual battery capacity (up to 100 A/Hr).
https://cpc.farnell.com/act-meters/612/battery-tester-sla/dp/IN07004
https://cpc.farnell.com/act-meters/612/battery-tester-sla/dp/IN07004
Hurricane
Well-known member
Following my comments above, these are the battery monitors that I would suggest:-
Battery monitors - Victron Energy
I have had one for about 13/14 years so mine hasn't got that nice Bluetooth interface.
But it has worked all through that period - even before I connected the solar panels.
It uses a "shunt" which is a device to measure the current flow in/out of the battery - the shunt is usually connected directly to the battery.
Some of those Victron monitors have an auxiliary input that can measure the voltage of (say) your engine battery.
But the auxiliary input on these Victron units don't incorporate a shunt so you are back to just measuring voltage (for the auxiliary battery).
If I were to replace mine, I would buy the BMV 712 Smart.
Battery monitors - Victron Energy
I have had one for about 13/14 years so mine hasn't got that nice Bluetooth interface.
But it has worked all through that period - even before I connected the solar panels.
It uses a "shunt" which is a device to measure the current flow in/out of the battery - the shunt is usually connected directly to the battery.
Some of those Victron monitors have an auxiliary input that can measure the voltage of (say) your engine battery.
But the auxiliary input on these Victron units don't incorporate a shunt so you are back to just measuring voltage (for the auxiliary battery).
If I were to replace mine, I would buy the BMV 712 Smart.
Refueler
Well-known member
Worth a few minutes reading manual ......
Martin_J
Well-known member
I'm happy with the Foxwell BT715.. (available from Gendan in the UK).
Seems to report available CCA (cold cranking amps) as well as battery State of Health, State of Charge and internal resistance and does it all quite quickly.
Seems to report available CCA (cold cranking amps) as well as battery State of Health, State of Charge and internal resistance and does it all quite quickly.
ss2016
Member
I use a Smartgauge. I thought long and hard about buying it because as far as I can see it should not work. The creator of it refuses to explain how it works. I noticed that people that owned them felt they were useful and now after a couple of years of use I find it very useful. I still don't see how it can work....but it gives me a very good indication of the state of charge.
Balmar the American company I noticed now sells a modified version so I presume they are convinced.
Balmar the American company I noticed now sells a modified version so I presume they are convinced.
Driver
Member
Many thanks for all of your replies to this and my parallel post. I think I will just fit solar panels, a job for next winter, and stop worrying about my batteries!
simonfraser
Well-known member
needs to be fit for purpose, depends on demand as much as the condition of the battery
as prev poster said install victron with shunt that will give you a good idea as to the voltage and what you use
i replaced one set recently as the voltage dropped too far to start my diesel hob mid winter without the engine on to charge
as prev poster said install victron with shunt that will give you a good idea as to the voltage and what you use
i replaced one set recently as the voltage dropped too far to start my diesel hob mid winter without the engine on to charge
Greg2
Well-known member
I fitted a Victron 712 Smart and I use the auxiliary function to monitor the mid-point of the battery bank. This alerted me to an installation error, which I rectified but the system continues to tell me that I have a problem when in actual fact the batteries are fine and doing what they should. I also find that I keep having to manually reset the state of charge indicator.
Chatting with a mate who originally trained as an electrician and has done lots of 12v work on his boats, including a complete re-wire on a project boat that he has gutted, and he says that he too installed a Victron monitor and he said it was often indicating that there was one problem or another when in fact everything was fine at a practical level. He got rid of it and simply keeps any eye on voltage in the batteries.
I will be checking that I have ours set up correctly to eliminate the possibility of operator/installer error but his experience was an intersting insight.
Chatting with a mate who originally trained as an electrician and has done lots of 12v work on his boats, including a complete re-wire on a project boat that he has gutted, and he says that he too installed a Victron monitor and he said it was often indicating that there was one problem or another when in fact everything was fine at a practical level. He got rid of it and simply keeps any eye on voltage in the batteries.
I will be checking that I have ours set up correctly to eliminate the possibility of operator/installer error but his experience was an intersting insight.
Hurricane
Well-known member
Have a look at this thread where we discussed my solar panel installation 7 years ago
I installed AGM batteries at the time but have now reverted to standard wet lead acid batteries.
Everything is working well.
Solar Panels
BTW Victron also provide good MPPT solar panel controllers - again with useful Bluetooth apps.
Hurricane
Well-known member
It is a long time since I installed mine but I don't understand the benefit of connecting the auxiliary input to the middle of the bank.
Greg2
Well-known member
Glad you replied because whilst my plan was to check the installation to make sure I had got it right your question prompted me to look it up. It turns out that the text manual I got with the unit wasn’t as clear as the Victron website version which clearly explains that it is for 24v ior 48v banks. With a 12v system I don’t have a mid-point to monitor
Doh!
Still, at least the alarm going off prompted me to carefully check the system resulting in identifying a poor connection so not a total fail!
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