How do I know if my battery's not charging?


If I'm using loads of accessories - e.g. extra lights, stereo, heated grips - how do I know if the battery is losing more charge than it's getting from the alternator? Is there an instrument I could fit which would tell me what's going on?

As you can tell from the way I've phrased the question I know as much about electrics as I do about astrophysics, so please don't get too technical!

Eurostar said:
If I'm using loads of accessories - e.g. extra lights, stereo, heated grips - how do I know if the battery is losing more charge than it's getting from the alternator?

When you press the starter button and nothing happens you will know :D :beer:
Many electrical systems operate on the basis of peak loads using the battery to supplement the output from the alternator on the basis that maximum demand won't be utilised for too long. As soon as the load drops (ie you turn something off) then the alternator is able to recharge the battery. Personally i wouldn't worry about it, you're not likely to suffer a flat battery whilst you're actually riding the bike. More likely is that inactivity will lead to poor battery life (ie not riding the bike frequently).

If your bike has factory fit heated grips it should have a higher alternator output. If not then you might conceivably have a problem but only if you're really loading the bike up. Even with heated grips, 2 pairs of extra front lights, extra side/tail lights and rear fog lights and an intercom i haven't had any problem with the electrical supply on my GS and i'll soon add a heated waistcoat to that lot.

If you're really worried about it borrow a clamp-on ammeter from someone in your area and you can do a quick, easy and safe check of the respective current draw and how well your alternator copes with it all. You can do the same with a conventional ammeter but it involves putting it in series (so all the current runs through it) which if you're not confident about what you're doing could be a mistake (understatement).

Hope this helps, but if not i'm sure many others will post and add more info,

Ta. It sounds like I'm worrying about nothing, even though I have the non-ABS 14 ampere battery rather than the 19 ampere one. But since you sound as if you know what you're talking about, here's another question: if I'm running accessories direct from the battery with the engine and ignition switched off, how do I know when it's time to turn them off because if I don't I won't be able to start the bike??
Eurostar, Voltmeter

Fit a voltmeter to monitor your battery, Farnells, Maplins or any good electronics store will have them, should be about £20 at rest the batt should read 12.5v or more when the engine is idling it should rise to 13.6v when at 2000 rpm or more should be at 14v so with everything on if it charges at 13.5v or more your'e OK and the alternator is working fine, if it starts to drop then its an indication of a wearing alternator and will give you the chance to rectify it before it fails, will also tell you if the belt has broke, assuming you don't hear the twang, you won't bump start one of these, not easily anyway.

So if your'e running accs from the battery keep an eye on the voltmeter and when it gets to 12.1 v start the engine.
Standard alt is 600watts largeer one for ABS & heated grips is 780watts.

A favourite trick of those with heated vests is to stand chatting with you while they have plugged their vest into your power point and when you come to go home the battery is too low, buggers !!

There is a tri colour led battery indicator, green, amber & red available at The Electrical Connection in the USA

Jim's reply is spot on. Although i'd be tempted to start the bike pretty soon after the volt reading dropped below 12.25V. Been to many a battery that didn't have enough charge left to turn the starter motor over EFFECTIVELY when it read less than 12.2V. As a form of automatic protection you can get battery monitors that will cut off the supply for electrical accessories (which are wired through it) when the voltage drops to a pre-determined level (don't ask me where from though - Maplins again ?). Be very careful though as again i have often been out to batteries that were dead because these battery monitors are often set too low (ie less than 12.25 Volts).

Bear in mind that a good, fully charged battery should actually read 12.5+ V, anything 12.2V-12.5V is only half charged and anything less than 12.2 is usually considered to be 'flat'. Another point to recognise but possibly not too important in our climate is the temperature. Below 0 degrees (centigrade) the efficiency and therefore output of a battery drops massively. 0 degrees = about 65% efficiency and it doesn't take long to get down to 50% with further drops in temperature. Hence you can see why plugging in your heated waistcoat would soon drop a 'healthy' battery down to a state where it can't start your bike (or better yet, someone elses' :D )

Issue with a Volt meter is that it AFTER the fact. An amp meter will show you charge or no-charge.....
True. Sounds like having both would be very reassuring - if they were fitted by someone who knew what they were doing.
More battery questions

Hope you guys can summon up the interest to carry on helping me with this - I'm now getting to the fun part!

I've put together an on-bike-stereo which I want to use when the bike's not running - e.g. when camping. In addition to a car type CD/tuner I have a separate amp which draws up to 15 Amps.

I've removed the battery from the bike, attached a voltmeter, and am running the stereo to see how much music I can have before the voltage is too low to start the bike.

Unfortunately I started with only 12V - I think because the bike has recently only had very short runs in London, always with full beam on, and I have the non-ABS model with the smaller battery. And it's 4 years old and the water in one of the cells is more than half an inch below the minimum.

Anyway, the stereo's been on for 2 hours and the voltage has only dropped by 0.2 at the most - which I'm pleasantly surprised by. I'll buy a new battery (because I'm off RTW and am renewing everything that wears out before I go) and hopefully then I'll end each day's riding with a much healthier voltage - 12.5V or more - which should allow me to have an evening's music and still leave a comfortable margin for starting the bike next morning. What do you reckon?

I'll be travelling alone in remote areas, so to give me an additional safety margin I'm planning to buy a solar panel - the Uni-Solar FLX5 which puts out up to 14 amp-hours per week. This doesn't sound like much to me. Let's say I've only got 11.5V and the bike won't start - will I grow old waiting for the solar panel to get me back up to 12V?

My immediate thought is that if you're going down this route (quite a high potential current draw, on the battery alone, whilst on a RTW trip) is to invest in a split-charge system. You mention that you haven't got ABS so you'd probably be able to mount a second battery under the tank. Wired CORRECTLY this would leave you the primary battery for starting/riding and the secondary battery for you evening music concert. You should always then have sufficient charge in the primary battery to start the bike and the secondary battery can charge up again when the bike is running.

Further points to note; - any battery undergoing the sort of prolonged discharge cycle that you are contemplating should really be a leisure battery type. Lead acid batteries don't cope well with prolonged discharge and rarely regain their full vigour.

Voltage readings can sometimes be misleading depending on the age/condition of the battery, the ambient temperature etc.

The PV panel doesn't sound like it will be of that much benefit to you.

15amps to drive the stereo is one HELL of an output. If that doesn't drain your battery in short-order nothing will. Are you sure you can't cope with just the headunit rather than a dedicated amp too? Most modern stereos will give 4x 40W which is plenty load enough for all but the "booyacker" subwoofer ground shaking brigade (or am i just too old?).

Doubt this will have helped. Probably just added to the confusion.

ps. don't forget to reset the motronic when you reconnect the battery.
Hmmm. Maybe I should never have started this!

I've read about split charge systems for desert-crossing Landcruisers and such like and I like the idea but am very reluctant to give up the space. That cubby hole where the ABS would be if I had one is reserved for hiding all those things that you aren't allowed to take into Algeria - GPS and satphone. But if you really think I must, I must. Where do I look for a leisure battery?

I take your point about the solar panel - my main justification for it is charging the laptop and satfone in a meltdown scenario where the bike's broken in the desert.

I know the amp is an indulgence...but I've bought it and I love it! You do need a fair bit of power if you want to hear the stereo on a bike which lacks a fairing to reflect the noise at you. And I think LOUD dance music will be the perfect accompaniment to big empty landscapes.

How do you reset the Motronic??
Mike Werner said:
Issue with a Volt meter is that it AFTER the fact. An amp meter will show you charge or no-charge.....

Not so. In actual pratice the voltmeter responds very quickly. Well with the 'small' batteries bikes have.

--- As for you overnight requirements well I look at it this way. Under the 'normal' conditions your bike will start with a one third charge in the battery .. say 6 AH... that should leave you with 6AH you can use over night... or around umm 6*12 = 72 watt/hours ... that is 72 watts for 1 hour or umm 36 watts for 2 hours .. Calculate how much energy (watthours) you will be using over night and you should have a fairly good idea if your battery will do the job. What is th eother third for? Well as the battery ages it loses capacity. So that third is a safety margin.

For a RTW I'd be using a hawker Oddessy type battery. Sealed, little self discharge and lotsa cold cranking amps.

--- Real 4WDs have 2 batteries with 2 alternators ... I've run such a set up. gives two independant electrical systems. Such a system adds too much weight to a bike. But is usefull on a camping vehicle with a fridge etc. how do I do the required sums? And do I need an ammeter?
Eurostar said:
I take your point about the solar panel - my main justification for it is charging the laptop and satfone in a meltdown scenario where the bike's broken in the desert.
The Sat Phone has its own battery. Always keep it at least half charged.

The laptop 'n amp are expendables. As is most clothing, camera.

The esentials are water, food, shelter. After that come the bike and petrol. Get these right and you don't really need anything else. You'll see once your in the desert. :cool:

We all tend to carry too much. Even Ted Simion who should know better. One guy I travelled with .. well we have a massive feed and burnt half his clothing ... that way two people could pick up his bike.
Eurostar said: how do I do the required sums? And do I need an ammeter?

No amp meter on the bike. But you might like to have a cheap DVM on the bike as a tool for fault finding. It should have a 10 Amp function. You can use that to measure the current drawn by your overnight gear.

You can get away from watthours here by just going staright to amphours ... multiply the current by the number of hours you think you'll need to have the gear on. Multiply this by, say, three and you get the battery capacity I think you should have. You could change the three to a two but you have less safety that way. Your call.

You will find once away from the trapings of 'civiliastion' that you may not want those things on anyway. I know I don't. A camp fire, a few mates and a port or two. :) You may have to settle for tea in dry places.
If you do all your 'planning/playing' with plenty of time to spare then you can get it all sorted out over here without too much hassle. No point buying an ammeter just to establish what current draw you're likely to use. You could calculate it all, but it is a bit of a pain in the arse. Easiest solution is to get hold of a decent clamp-on ammeter and just run through all your worst-case scenarios to see how much drain you have on the battery.

Personally i would take a multi-meter with me on the trip (DVM - as previously suggested) but you do need to know how to use it or else it'll be more wasted weight and possibly add to the confusion.

I have all manner of 'shiny' electrical things, including a good clamp-on ammeter so if you can't borrow one more local then give me a shout and i'd be glad to help out. I'll be in the Abingdon/Oxford area for a few days over Xmas so could meet up somewhere to assess your attempt to drain the national grid.

You don't have to go to the lengths of fitting a second full-size battery for split charge system. Nor need it be expensive. Could just have a small battery wired in parallel with an isolator switch. Full split-charge can automate everything but not really necessary.

If you check out the current drain to your satisfaction you might find you don't even need it at all.

"PPPPPP" = prior preperation prevents p*ss poor performance.

As always there aren't any definitive answers to your problem, just lots of subjective ones. So no NEED for a split charge system. Just whatever gives you piece of mind and a good chance of success with minimal effort.


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