What kind of multimeter do I need to do an engine battery test?

GeeCee

GeeCee

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I'm thinking of buying a multimeter to do a battery test on my engine battery to see what's causing it to lose power 3 days after charging, i.e. by testing the power being drawn and pulling out fuses to identify the culprit.

Looking online it seems you can pay anything from £8 to £160. Some of the cheaper multimeters seem to have a maximum of 10 amps (assuming I've understood their purpose correctly) but some of the fuses on the Fiat are for 20 amps. Can someone recommend one that covers 20 amps at a reasonable price, e.g. up to say £50.
 
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For that purpose you might be better with a clamp amp meter otherwise to measure current flow with a multimeter you have to disconnect the circuits and put the meter in series.
 
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GeeCee said:
I'm thinking of buying a multimeter to do a battery test on my engine battery to see what's causing it to lose power 3 days after charging, i.e. by testing the power being drawn and pulling out fuses to identify the culprit.

Looking online it seems you can pay anything from £8 to £160. Some of the cheaper multimeters seem to have a maximum of 10 amps (assuming I've understood their purpose correctly) but some of the fuses on the Fiat are for 20 amps. Can someone recommend one that covers 20 amps at a reasonable price, e.g. up to say £50.
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If it takes 3 days to discharge your battery then that is 50Ah / (3 days x 24 hours) = 0.69Ah being lost. Change the figures to suite. I used a 100Ah battery (with 50% usable) over 3 full days.

If your battery was losing 10A then it would be flat in 5 hours.
If you battery was losing 20A then it would be flat in 2 hours.

So a 10A multimeter should be fine. However, if you are not sure. You could always put an inline fuse in the lead to add additional protection.

I suspect if it is 3 days then your losses are likely to be less than 1amp


PS: If this is your first time using a multimeter for current. Then a cheap one might be advised as it is a common rookie error to put the probes across the battery in Amp mode and blow the internal fuse or blow the multimeter up.
 
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GeeCee said:
I'm thinking of buying a multimeter to do a battery test on my engine battery to see what's causing it to lose power 3 days after charging, i.e. by testing the power being drawn and pulling out fuses to identify the culprit.
Some of the cheaper multimeters seem to have a maximum of 10 amps
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Click to expand...

The meter with 10amp max will be fine as with everything turned off it's highly unlikely that there'll be a current drain that exceeds anywhere near 10amps.
GeeCee said:
some of the fuses on the Fiat are for 20 amps. Can someone recommend one that covers 20 amps at a reasonable price, e.g. up to say £50.
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If you will only be testing the fuses for continuity with everything turned off and the engine stopped rather than measuring the current flowing through them with the engine running a 10amp max range will be fine. Regardless of the fuse rating the only current flowing through them when testing with the meter for continuity will be from the meter's own small internal battery.
I've been using the same cheap ten quid ones for maybe ten years for all the testing that I've needed to do, having one in the m/h, one in the car and another in my motorbike workshop.
 
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Gromett said:
If it takes 3 days to discharge your battery then that is 50Ah / (3 days x 24 hours) = 0.69Ah being lost. Change the figures to suite. I used a 100Ah battery (with 50% usable) over 3 full days.

If your battery was losing 10A then it would be flat in 5 hours.
If you battery was losing 20A then it would be flat in 2 hours.

So a 10A multimeter should be fine. However, if you are not sure. You could always put an inline fuse in the lead to add additional protection.

I suspect if it is 3 days then your losses are likely to be less than 1amp


PS: If this is your first time using a multimeter for current. Then a cheap one might be advised as it is a common rookie error to put the probes across the battery in Amp mode and blow the internal fuse or blow the multimeter up.
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Thanks. Sounds like a cheap one is what I need.
 
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Spriddler said:
The meter with 10amp max will be fine as with everything turned off it's highly unlikely that there'll be a current drain that exceeds 10amps.

If you will only be testing the fuses for continuity with the engine stopped rather than measuring the current flowing through them with the engine running a 10amp max range will be fine.
For maybe ten years or more I've been using cheap ten quid ones for all the testing that I've needed to do with one in the m/h, one in the car and another in my motorbike workshop.
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Thanks I'll get a cheap one then.
 
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If you have easy access to the fuses the easiest way to check current is at the fuse holder.
Switch the meter to amps, remove the fuse in the circuit to be tested then Stick one probe in one side of the fuse holder and the other in the other side.
Doesn't matter which way round with a digital meter as if it's the wrong way round it will show a - before the number/s.....if it's right just numbers will be shown.
Just a cheap basic meter will suffice.
 
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pappajohn said:
If you have easy access to the fuses the easiest way to check current is at the fuse holder.
Switch the meter to amps, remove the fuse in the circuit to be tested then Stick one probe in one side of the fuse holder and the other in the other side.
Doesn't matter which way round with a digital meter as if it's the wrong way round it will show a - before the number/s.....if it's right just numbers will be shown.
Just a cheap basic meter will suffice.
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Very good suggestion. I hadn't thought of that. Nice one (y)
 
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Gromett said:
Very good suggestion. I hadn't thought of that. Nice one (y)
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Some things will maybe take power while they boot up though, my car's terrible for it. I'd put the clamp meter round the battery connection, let everything settle down for an hour and see what's happening 👌

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Richard n Ann said:
Some things will maybe take power while they boot up though, my car's terrible for it. I'd put the clamp meter round the battery connection, let everything settle down for an hour and see what's happening 👌
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That is the way I would normally do it, but using a normal meter not a clamp meter.

I had a cheap DC clamp meter in the past and it had lousy accuracy under 1Amp. Under 1 Amp it would basically indicate if there was current flowing or not.

Not sure if things have improved since then, but that was 15/20 years. I haven't considered a clamp meter since tbh.
 
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GeeCee said:
I'm thinking of buying a multimeter to do a battery test on my engine battery to see what's causing it to lose power 3 days after charging, i.e. by testing the power being drawn and pulling out fuses to identify the culprit.

Looking online it seems you can pay anything from £8 to £160. Some of the cheaper multimeters seem to have a maximum of 10 amps (assuming I've understood their purpose correctly) but some of the fuses on the Fiat are for 20 amps. Can someone recommend one that covers 20 amps at a reasonable price, e.g. up to say £50.
Click to expand...

If you want to use pappajohn method in the fuse box but want to monitor for a while. Get a set of leads for your meter that has the clips on it like these. You can then use normal crimp spade connectors with the plastic cut off to insert into the fuse holders and clip the meter leads to. You can then leave it in situ and monitor.

BUT. If using this method I would fit an inline fuse because you are taking the cars fuse out of the circuit.
 
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Gromett said:
had a cheap DC clamp meter in the past and it had lousy accuracy under 1Amp. Under 1 Amp it would basically indicate if there was current flowing or not.
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Yes know what you mean, the uni-t one is pretty good though, one of the best I've had for small readings.
 
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I got a UNI-T UT210E for £45 on Amazon six months ago for a similar purpose.

Brilliant bit of kit, and accurate at milliamp DC currents. Reads up to 100A DC or AC.

Main limitation is the size of the clamp, but luckily it just fitted over the heavy duty cables on my batteries.
 
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Another vote for the UNI-T UT210E(y)

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Make sure it has dc amps capability as previously mentioned 👍
 
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pappajohn said:
If you have easy access to the fuses the easiest way to check current is at the fuse holder.
Switch the meter to amps, remove the fuse in the circuit to be tested then Stick one probe in one side of the fuse holder and the other in the other side.
Doesn't matter which way round with a digital meter as if it's the wrong way round it will show a - before the number/s.....if it's right just numbers will be shown.
Just a cheap basic meter will suffice.
Click to expand...
You really don't want to be messing about removing fuses from the battery connections in a modern vehicle I wouldn't risk it with all the ECU's that love throwing wobbles.
I use a U210E clamp meter as well got to be the best 30 quid I ever spent.
 
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GeeCee said:
I'm thinking of buying a multimeter to do a battery test on my engine battery to see what's causing it to lose power 3 days after charging, i.e. by testing the power being drawn and pulling out fuses to identify the culprit.

Looking online it seems you can pay anything from £8 to £160. Some of the cheaper multimeters seem to have a maximum of 10 amps (assuming I've understood their purpose correctly) but some of the fuses on the Fiat are for 20 amps. Can someone recommend one that covers 20 amps at a reasonable price, e.g. up to say £50.
Click to expand...
Here's a quick guide to specific battery testers (i.e kit designed to test various aspects of 6 and 12v battery maintenance) https://yourcar.co.uk/best-battery-tester/
 
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pappajohn said:
If you have easy access to the fuses the easiest way to check current is at the fuse holder.
Switch the meter to amps, remove the fuse in the circuit to be tested then Stick one probe in one side of the fuse holder and the other in the other side.
Doesn't matter which way round with a digital meter as if it's the wrong way round it will show a - before the number/s.....if it's right just numbers will be shown.
Just a cheap basic meter will suffice.
Click to expand...
What if the fuse you're testing is rated at 20 amps, then would the 10 amp meter (as per my original question) still work, or would it damage the meter.

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GeeCee said:
What if the fuse you're testing is rated at 20 amps, then would the 10 amp meter (as per my original question) still work, or would it damage the meter.
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Testing fuses you are measuring resistance it's nothing to do with current you can use any meter.
 
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Just smiffy said:
What about this one…..😎

www.ebay.co.uk

Digital Clamp Meter AC/DC Voltage AC Current Multimeter LED Temp Volt Amp Tester | eBay

Find many great new & used options and get the best deals for Digital Clamp Meter AC/DC Voltage AC Current Multimeter LED Temp Volt Amp Tester at the best online prices at eBay! Free delivery for many products.
www.ebay.co.uk
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It says AC/DC Voltage AC Current. That means it will measure DC Voltage, but won't measure DC Current. It's great for electricians who work with Mains AC all the time, but no good for vehicle electrics because they are all DC. There's a lot of clamp meters like this, you need to definitely check it can do DC Current (amps).

The one I always take in the motorhome is the UNI-T UT210E.
 
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autorouter said:
you need to definitely check it can do DC Current (amps).
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The OP's is fine for DC current.

Test meter.JPG


This is mine which is identical to the OP's and measures DC current.


Note that max DC current is 10 Amps, but you can test any rating (20 amp, 50amp etc.) of fuse for continuity after removing the fuse because the only current passing through the fuse will be the small current from the meter's own internal battery.

The AC and the DC ranges on the test meter dial are shown by the appropriate symbol :
Test meter voltage symbols.JPG
 

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Great but easy for a novice with electrics to make a mistake. In the OP the desire was to measure current draw to see what’s flattening battery. The right thing to buy was a current clamp….
 
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