Z1OwnersClub GB

Got out for a couple of rides three weeks ago, no problems with the bike. Last week rode it on Friday to the Scottish bike show. On Sunday at the end of the show tried to start it, the battery was flat, managed to kick start it. Halway home it cut out and wouldn't even kick start. The battery shows 12.87 when fully charged, when the starter button is pressed it struggles after a few seconds to turn and the multimeter shows 8.5. The optimate indicates the battery is fine and charges it very quickly. It obviously looks like the battery is dead the only thing which makes me question this is that the battery is a Yuasa AGM battery, it's only two years old, kept in the house over winter and routinely maintained. In forty years I've never had a battery fail in this way, have I just got a dud battery or am I missing something? Cheers

The Battery 'Charging' and the Battery actually 'Holding' that charge are two very different things.

Have you checked the voltage at the battery with the engine running around 3K revs?. Should be around 13.5-14.5 volts. Any more you could have a Reg/Rec problem putting to much charge into the battery thus frying the plates.

Cheers Garry, engine running hits 14.5 volts, replaced the regulator/rectifier and stator last year and I''ve replaced most of the wiring loom recently. Looks like I may just have a duff battery

What bike do you have?

as a z1/900 or even a z1000 should run with out a battery, not to be advised doing it for long as long as you dont have electronic ignition

the battery could be a problem made by the real fault, or you have a dead short in your battery which may well be a answer to your problem, Optimate should show red if that was the problem

Agm batteries do tend to totally fail,not like the old lead acid types which fade gradually.

Cheers Harty, my Z1000 has Dyna coils and electronic ignition, Optimate shows fully charged. Paul, that's handy to know, I've never had a battery which has failed so quickly so I must just have a duff one.

Seems that Yuasa only offer a 12 month warranty, which probably says something about how long they're expected to last.
I don't have shares in Motobatt & am not plugging them, but I did notice that they have a 2 year warranty depending on where you buy them, some places only offer 12 months.
https://www.ebay.co.uk/itm/MOTOBATT-MB1 ... 1438.l2649

When the Optimate gives you battery condition, it is based entirely on battery voltage,so 12.87 would be fully charged. Voltage is probably the least accurate way of checking battery condition, it probably has sulphated plates and if you measured the current it is absorbing it would be very low, so consequently unable to give your starter motor the power it needs. One of the biggest cause of battery failure is lack of use, sound familiar.

GS, which owns and is the parent company to Yuasa, offer a two year warranty on all their batteries.

In the OEM market, they are branded as GS-Yuasa.

GS batteries are generally cheaper than Yuasa too.